The present invention relates to heat transfer labels. More particularly, the present invention relates to heat transfer labels printed on a temporary carrier film or paper for application to various substrates, followed by UV curing the label to provide chemical and abrasion resistance.
Labels are in widespread use in most every industry. For example, labels are used to transfer indicia onto all manner of durable goods consumer items ranging from cell phone cases to golf club shafts. Typically, labels consist of thermoplastic colors capable of being heat activated in order to adhere to substrates upon application of heat and pressure. Many of these items to which the indicia are applied are rigid or semi-rigid, thus allowing the label transfer to be carried out using heat transfer methods.
It is of utmost importance that the indicia or marking transferred to the item be of a high quality. In many instances the item is one that is intended to be used for a long period of time. For example, cellular telephones are intended to last for at least a number of years, as are golf clubs. To this end, the indicia printed (e.g., the manufacturer's name, trademark or the like), should be a long-lasting, difficult to abrade and resistant to chemical and environmental degradation.
In order to achieve these operating objective, typical heat transfer labels for substrates such as graphite and many plastics currently require a bake cycle of approximately 60 minutes at 200° F. This is necessary to achieve the chemical and abrasion resistance desired, but must be balanced against (i.e., avoidance of) damage to the substrate due to excessive heat. Likewise, heat transfer labels for glass and metal substrates also require an extended bake cycle at elevated temperatures (e.g., 400° F. for a period of about ten minutes), after the labels have been applied to the substrate to achieve good chemical and abrasion resistance.
In addition, many of the known high quality heat transfer labels are not sufficiently stable prior to application and curing. That is, the labels can have a relatively short shelf life, and as such may not be of the desired quality after a prolonged storage period.
Accordingly, there is a need for a high quality heat transfer label that has high chemical and abrasion resistance. Desirably, such a label is easily made (e.g., printed), using readily commercially available materials. More desirably, using such a label, indicia is transferred to an item or object by a process that substantially reduces the curing cycle time and heat transferred to the item. Most desirably, such a label is stable and has a prolonged shelf life.